As usual when Adam Block produces galaxy images, the color information they convey is absolutely fascinating.
NGC 3169 and NGC 3166 certainly look like an old cantankerous married couple who have flared up in spectacular outbursts during their long life together. In their youth, they danced a violent tango, spitting fire and brimstone and exploding in blotches of rosy red nebulae and brilliant blue young stars. Now, however, they are tired and spent, remembering old glories as their old fires grow yellow and dim.
Look at NGC 3166! Only wisps remain of its once mighty dust lanes. Remnants of a blue ring can be seen encircling its innermost yellow center, but not a single young cluster can be seen among its well-mixed middle-aged stellar denizens. NGC 3166 has an oblong outer ring, typically brighter "at its oblong ends", making this structure look a bit like a bar. Again, no signs of clusters can be seen anywhere. But the yellow center burns brightly, harboring the consequences of its youthful antics, a supermassive black hole.
The companion of NGC 3166, its old mate, NGC 3169, retains more of its youthful power. The ashes of its many outbursts, a thick dust lane, winds around its bulge, tosses and turns in mighty cascades and prodigiously reddens the light from its center. Young stars are still born from this dust, as can be seen from the obvious clusters and many small splotches of pink, the cradles of the newborn stars. Still, the fireworks of star formation here are probably nothing compared with what they were when the galaxies first met, when so much of their gas and dust was available for star formation, and so little of it had been funneled into the galaxies' ever-growing and ever hungrier central black holes.
Two dwarf galaxies can be seen to the right of NGC 3166. They are very different; the lower one, NGC 3165, has a high surface brightness, is completely dominated by the light of young blue stars, and it is still actively forming stars. Four or five pink emission nebulae are spread over the face of this galaxy at fascinatingly regular intervals. Its shape is reminiscent of a dancing child, with a bar-like "body" and incipient spiral arms that could be the galaxy child's head and legs.
The upper dwarf galaxy has such a low surface brightness that my software has no name for it. It is diaphanous, delicate and ethereal, a ghostly apparition in the heavens. But this faint dwarf galaxy has one thing in common with its bright blue dwarf "colleague": both have small bright blue nuclei.
If you think I have sounded unnecessarily solemn, sounding as if I was reading a poem, well, Adam Block's galaxy images do that to me!